Heavier vehicles, e.g. trucks and buses, usually have spring-suspended cabs that move in relation to the chassis of the vehicle whereby these vehicles have a lower steering shaft in the form of a telescopic shaft, which automatically may alter its length during the travel of the vehicle, between the steering wheel and the steering gear as the steering wheel is lockable in its axial direction to the cab of the vehicle whereas the steering gear is fixed to the chassis of the vehicle. The telescopic shaft may be of different kinds but usually comprises an outer shaft and an inner shaft that are axially movable in relation to each other but locked in relation to each other in the direction of rotation of the shaft in order to thereby be able to transfer torque from the steering wheel of the vehicle to the steering gear. General types of telescopic shafts are ball-telescopes with at least two rows of balls between the inner and the outer shaft where the rows of balls are symmetrically arranged around the periphery of the inner shaft and where the balls may both roll and slide, ball-telescopes with circulating balls between the inner and the outer shaft where the balls always roll, such as e.g. is shown in U.S. Pat. No. 3,995,916, needle bearing roller based telescopes with needle rollers between the inner and the outer shaft and with prestress and load limiting devices, and splines-telescopes without balls or rollers where surfaces slide against each other when altering the length of the telescope.
One example of a telescope is shown in U.S. Pat. No. 6,343,993 B1, which shows a telescope where resilient elements on a first shaft press divided ball races against the balls which in turn are pressed against a second shaft.
A problem with a telescope as mentioned above is that heavy demands for a long stroke of the telescopic shaft are put forward for trucks with tiltable cabs in order for the cab to be able to be tilted. E.g., the telescopic shaft according to U.S. Pat. No. 6,343,993 B1 above is designed for short strokes of the order of 30 mm. As the balls of the telescope are spring-loaded, sliding of the balls is prevented wherefore ball races that are of the same length as the stroke are required in order for the balls to be able to roll over the whole stroke. This causes problems with the long strokes that are required for tiltable cabs.
A problem with ordinary ball-telescopes where the balls may both roll and slide is that narrow tolerances are required over the entire stroke which causes problems with the long strokes that are required for tiltable cabs.